This invention relates to an excavating tooth assembly and, more particularly, in which an assembly consisting of point, adapter and wear cap has a unique stabilizing relationship between the elements so as to resist heavy forces.
Since the turn of the century, the practice in the excavating art has been to employ excavating teeth with replaceable tips known as "points". By replacing the points on the adapter from time to time, the penetrating ability is maintained. Often, an adapter will outlast five or more replacement points.
With the frequency of replacement, this necessitated the provision of releasable locking means and, for many years, the locks were staunch in order to withstand the forces tending to draw the point off of the adapter. For the most part, the adapter was equipped with a wedge shaped, forwardly extending nose received within a correspondingly contoured socket at the rear of the point. In order to mitigate the stresses on the locking pin (which generally extended vertically through aligned openings in the point and adapter nose), the phenomenon of secondary stabilization was employed. This was featured in U.S. Pat. No. 2,483,032 and achieved through the provision of rearwardly extending tongues or ears on the point which made it within corresponding recesses in the adapter. Thus, a loading on the end of the point would cause pivotal movement of the point on the adapter nose and bring secondary surfaces, i.e., those other than the confronting faces of the socket and nose, into engagement.
Although this type of stabilization was effective for many years in two-part teeth, a vastly superior type of stabilization was taught in U.S. Pat. No. 3,079,710. An important feature in that patent was the provision of stabilizing surfaces at the apex of the nose and socket on opposite sides of the longitudinal axis of the tooth, i.e., the path of movement in installing the point on the adapter. This principle of operation of the stabilized tooth of the '710 patent involved longitudinally spaced pairs of bearing surfaces so as to uniquely resist pointremoval forces. It will be appreciated that even a pure beam loading, i.e., a vertical force, would develop a forward component in the ordinary tooth extending parallel to the associated wedge faces on the nose and socket--thereby developing a negative thrust tending to remove the point from the adapter.
Although this principle has functioned quite satisfactorily for almost 20 years, it never was used to advantage in teeth equipped with wear caps. It will be appreciated that although the point can be replaced from time to time, the upper surface of the adapter is subject to almost as much wear as the point--as by virtue of the earth passing thereover and developing an abrading action. An early version of a wear plate or cap for an adapter is seen in U.S. Pat. No. 1,918,841. Over the years various forms of wear caps were provided to cover the upper surfaces of the adapter such as those seen in U.S. Pat. Nos. 2,762,139; 2,896,345; 3,020,655 and 3,082,555. However, in all of these cases, there was no cooperative action between the point and wear cap--except the normally expected cooperation of the point serving to hold the wear cap in place--and this only in certain instances. In other words, the point had to be removed from the adapter before the wear cap could be removed from the adapter.
According to the invention, a novel cooperation is provided between the wear cap and point wherein these two elements function to provide secondary stabilization. In the preferred embodiment, the wear cap is equipped with forwardly extending tongues which are received within correspondingly contoured recesses in the point rear and which serve the purpose of secondary stabilization. No analogous teaching has been found in the art. The concept of providing recesses in the point rear to receive tongues (as from the adapter) has been known for many years--see U.S. Pat. No. 1,845,677. More recently, a point was equipped with a hook-shaped notch to receive a corresponding hook on something akin to a wear cap, i.e., a ripper shroud as seen in U.S. Pat. No. 3,999,614. However, this type of locking engagement was well known in the shroud art as seen in U.S. Pat. No. 3,621,594. In any event, there was no cooperation to provide stabilization of the form found advantageous in minimizing shearing stresses on the lock holding the point and adapter in assembled condition.
According to the invention, the point and adapter have primary bearing surfaces provided at the apex of the socket and nose. Although in accordance with established practice it is advantageous to have the socket in the nose (so as to minimize the amount of throw away metal), the nose and socket may be interchanged on the point and adapter. Thus, the means for coupling the point and adapter include a structure such as a nose or socket and the complement or negative thereto.
The above-mentioned bearing or stabilizing surfaces are disposed on opposite sides of the predetermined path of mounting, i.e., the tooth longitudinal axis. Further, the point has joint means in the form of a recess or tongue provided in the rear of each sidewall into which a forwardly extending tongue or rearwardly extending recess (i.e., the complement or negative) extends from the wear cap--thereby providing a secondary set of stabilizing surfaces. Advantageously, the tongues and recesses providing these secondary stabilizing surfaces are vertically offset from the longitudinal mounting axis and the preferred embodiment provides two sets of recesses in each point sidewall so as to render the point readily reversible. This also cuts down on the amount of throw-away metal when the point is to be replaced.
In the prior art tooth having rearwardly-existing tongues to provide secondary stabilization, the recesses in the adapter often became worn or "peened" because of the contact of the tongue therewith. This meant that as the adapter aged, poorer and poorer secondary stabilization was provided--even with the new points that were installed from time to time. Building up of the worn areas of the adapter was not an attractive alternative because of the difficulty of welding the special strength alloys, particularly in the field.
This then underscores another significant benefit of the invention--the ability to renew the stabilizing means independent of the adapter. Normally, the wear cap is replaced with every second point so that even over the prolonged life of the adapter, the joint means and complement thereto forming the secondary stabilizing surfaces are maintained in most effective condition by frequent renewal.
Other objects and advantages of the invention may be seen in the details of the ensuing specification.